"We think it works through some kind of subtle parenting change ... in the end we actually want babies and young children to listen to their body and eat when they're hungry."
Sleep lessons made no difference to the duration or quality of the sleep.
The study involved 802 Dunedin families split into groups that received different levels of help and advice.
One group received additional support around food, exercise, and breast-feeding; another group received the sleep programme, and some families received all of the interventions.
The extra advice around food, activity, and breast-feeding resulted in no change in obesity levels, which surprised the researchers.
The study co-leader was Prof Rachael Taylor, the director of the Edgar Diabetes and Obesity research centre.
Families in the sleep group had one class before the baby was born, and a personal visit from a sleep nurse when their baby was three weeks old. Some families requested extra help if their baby still had difficulties sleeping after six months of age.
The two-year Prevention of Obesity in Infancy study has been published in the journal Pediatrics.